Squirrel Servers Manager (SSM) provides a robust system for passing variables (known as "extra vars" in Ansible terminology) to your playbooks during execution. This allows for dynamic and customized automation.

In a Nutshell (🌰)

• SSM passes variables to playbooks using Ansible's --extra-vars mechanism.
• Handles transformation from SSM's format to Ansible's expected JSON format.
• Supports complex data structures and secure handling of sensitive values.

Passing Extra Variables

When you execute a playbook through SSM (e.g., via Stacks or Automations), you can provide variables that will be passed to the ansible-runner using the --extra-vars command-line argument. SSM uses internal services (like ExtraVarsService and ExtraVarsTransformerService) to manage this process.

Transformation

SSM often stores or receives variables in a specific format (e.g., an array of key-value pairs via its API). The ExtraVarsTransformerService is responsible for converting this format into the JSON string format expected by Ansible's --extra-vars.

Example internal transformation logic (conceptual):

// Example of how SSM might prepare the --extra-vars argument
function getExtraVarsArgument(extraVars?: API.ExtraVar[]): string {
  if (!extraVars || extraVars.length === 0) {
    return '';
  }
  
  // Transform the API format (e.g., [{key: 'myVar', value: 'myVal'}]) 
  // into an Ansible-compatible object (e.g., { myVar: 'myVal' })
  const ansibleVars = transformToAnsibleObject(extraVars);
  
  // Return the formatted command-line argument
  return `--extra-vars '${JSON.stringify(ansibleVars)}'`;
}

Key Features

• Format Transformation: Converts variables from SSM's internal/API format to the JSON structure Ansible requires.
• Secure Value Handling: Integrates with SSM's credential management to handle sensitive variables marked for vault encryption.
• Data Structure Support: Allows passing complex data types like lists, dictionaries (objects), booleans, and numbers, not just simple strings.
• Validation: May include validation steps to ensure variable formats are correct before passing them to Ansible.

Variable Precedence

Remember that variables passed via --extra-vars have the highest precedence in Ansible, overriding variables defined in inventories, playbooks (vars sections), or roles. For a full understanding of Ansible's variable precedence rules, consult the official Ansible documentation on variable precedence.